New technology,which traces the pupils as they draw the shape of letters,could make it possible for paralysed patients to use their eyes to project handwriting onto a screen.
Although our eyes are capable of smoothly tracking moving objects,it is usually impossible for us to make such controlled and precise movements at will.
As a result,paralysed patients can currently use eye-reading devices to point towards a particular object on a screen,but are unable to communicate freely by drawing the outlines of letters.
However,now a French researcher claims to have discovered a way of tricking the brain into thinking it is watching a moving object,allowing the patient enough control to trace letters,numbers and even write their signature.
“Contrary to the current belief,we show that one can gain complete,voluntary control over smooth pursuit eye movements. The discovery also provides a tool to use smooth pursuit eye movements as a pencil to draw,write,or generate a signature, the Telegraph quoted Jean Lorenceau from the Universite Pierre et Marie Curie-Paris as saying.
The technique relies on an illusion caused by a flickering screen filled with a random array of static discs varying in contrast.
When the eyes are fixed on the screen the discs appear faint and still,but when the patient shifts their gaze the stationary field appears to move with them in the same direction,rather than seeming to move in the opposite direction as would normally happen.
A ring of coloured dots also follow the eyes to enhance the effect,duping the brain into thinking the eyes are following the dots and not the other way around.
According to Lorenceau,after three half-hour training sessions healthy volunteers could direct their eyes in any direction,and further training allowed them to write words at a rate of 20-30 characters per minute,similar to cursive handwriting.
After brief training,participants gain volitional control over smooth pursuit eye movements and can generate digits,letters,words,or drawings at will, he wrote.
When the contrast between the discs was high the exercise proved tiring for participants,but low contrast conditions were more favourable,he added.
Under low contrast conditions,participants perceive a faint motion flow,as snowflakes moved by the wind,and can smoothly move their eyes for long periods of time, he added.
The study has been published in the Current Biology journal.